Successful Husbandry and First Breeding of Varanus juxtindicus ...

More documents

Recommendations

Info

was important to control the feeding because juvenile V. juxtindicus can hurt each other severely. If necessary, the young monitors were fed separately. Development of the Juveniles Body Proportions and Weight The development of the juveniles during the first year is documented in Diagrams 1 through 5. As expected, the increase in body mass showed the highest values (Diagram 1). While the hatchlings weighed 23.1 g on average at birth, after a year their weight had increased by a factor of 10. The values of the increase in snoutvent length in all specimens were similar (Diagram 3), probably because the quantitatively and qualitatively equal food allowance enabled a similar development. After one year, snout-vent lengths varied between 20.7 and 27.4 cm (mean = 24.0 cm). In contrast, the growth in tail lengths shows a noticeably divergent progress (Diagram 4), a physiological feature which is apparently genetically fixed and thus not affected by targeted feeding. In addition, variation in growth rates may be related to the sex of the specimens, but this information was not available. Correspondingly, the clearly divergent values of the total length are foremost the result of the individually divergent increase in tail lengths (see BIAWAK VOL. 3 NO. 4 117 Diagram 2). Regarding the relation between snout-vent length and tail length, juveniles of V. juxtindicus hatch with relatively short tails – common among all monitor species studied on this variable (Mertens, 1942; Horn and Visser, 1991). The development of the head and body with the essential organs claims the maximal space in the egg (Horn and Visser, 1991). Within the first weeks, the relation of snout-vent to tail was clearly shifted in favor of tail length (Diagram 5). At six months, the highest relative values loomed and, at the same time, the highest discrepancy between absolute maximal and minimal amount. Up until the first year, the relative tail length decreased again marginally, while maximal and minimal values approximated strongly (Diagram 5). At that time, the tail length was approximately 1.5 times the snout-vent length. This proportion between tail length and snout-vent length is also found in other monitor species (e.g., V. indicus and V. salvator), which are predominantly terrestrial or aquatic, while arboreal species have much longer tails and desert species often have shorter tails (Mertens, 1942; Horn and Visser, 1991). Change in Color Pattern Dorsally, hatchlings of V. juxtindicus show a dense pattern of small and large whitish spots arranged in Diagram 5. Increase in mean SVL:TL ratio of V. juxtindicus offspring (n = 8) during the first year.
118 WESIAK AND KOCH - HUSBANDRY AND BREEDING OF VARANUS JUXTINDICUS irregular transverse rows on a dark background. On the tail, the spots form a regular pattern of alternating transverse rows of larger and smaller spots respectively (Figs. 3 and 14). After the first molting at about two months, the spots become yellowish on the body. Laterally on the tail, some scattered ocelli are formed (Figs. 18A and B). Between the second and third molting, at about six months, the yellow coloration on the head, neck and limbs is intensified. On the back and tail, the smaller yellowish spots changed to a faint pattern of turquoise lines and distinct ocelli (Figs. 1, 18C and D). The underside of the body also showed distinct ocelli (Fig. 17). After the fourth molting at the age of about one year, the head, neck, and limbs still exhibit the brightest colors. The dotted color pattern has changed into a reticulated yellowish-green pattern interspersed with black markings (Figs. 19A and B). At the age of about two years, the juveniles of V. juxtindicus resemble the adults. The original color pattern of large whitish spots has dissolved into a homogenous and dense mottling of yellowish-green and orange small dots on a dark background. Only along the tail do the small dots still form thin and short transverse bars. The limbs are covered with yellow scales which have dark margins (Figs. 19C and D). A B C A significant ontogenetic change in color pattern from juveniles to adults within the same species is a rather common phenomenon in monitor lizards (Mertens, 1942). The occupation of different ecological niches during specific life stages within the same habitat may be responsible for the phenomenon. For instance, juveniles of V. komodoensis Ouwens, 1912 and V. bengalensis (Daudin, 1802) exhibit a vivid pattern of spots. With this camouflaged coloration, juvenile monitors are predominantly arboreal until they grow up to avoid pressure by various predators – including adult conspecifics (Auffenberg, 1981; Karunarathna et al., 2008). In the case of V. juxtindicus however, no statement can be made at the present time for the process of color change due to a lack of field observations in the their natural habitat. A study about ecological and spatial niche partitioning by Philipp (1999) showed that V. indicus on New Guinea is not a very specialized species. This close relative of V. juxtindicus inhabits mangrove swamps, costal forests, inland forests along rivers, and lower mountain forests. Niche partitioning into different microhabitats by distinct age groups could not be inferred in the study area on Irian Jaya, New Guinea (Philipp, 1999). Fig. 18. Ontogenetic change in color pattern of dorsum and tail after two (A, B), six (C, D) months. Note the roundish base of the tail lacking a dorsal double keel as characteristic for V. juxtindicus. Photographs by Klaus Wesiak D
Page 1 and 2: Biawak, 3(4), pp. 106-121 © 2009 b
Page 3 and 4: 108 WESIAK AND KOCH - HUSBANDRY AND
Page 5 and 6: 110 Housing WESIAK AND KOCH - HUSBA
Page 11: 116 WESIAK AND KOCH - HUSBANDRY AND

Successful Husbandry and First Breeding of Varanus juxtindicus ...

Create successful ePaper yourself

Delete template?

Save as template?